Blasting cap



Sept. 10; 1940.

w. DE c. fCRjATE'R BLASTING" CAP Filed Feb. 14, 19 59 Fla-2 WILLARD- DE 0. CRATER INVENTOR ATTORNEY Patented Slept. 10, 13 40 stares BLASTING CAP corporation of Delaware Application February 14, 1939; Serial No. 256,286

12 Claims.

This invention relates to an improved firing device and more particularly to an improved blasting cap of the type containing a base charge and a priming charge.

It is well known that the commercial firing de vices used by the art may be either closed shell electric blasting caps or open shell fuse blasting caps. Heretofore these two types of blasting caps have been prepared by using a metal shell containing a unit explosive charge .of an initiating explosive, for example mercury fulminate, lead azide, or diazodinitrophenol either alone or in admixture-with an oxidizing agent such as potassiumchlorate or the like. Further these two types of blasting caps have also been prepared by using a non-initiating base charge, for example, tetranitromethylaniline, nitrostarch, trinitrotoluene, picric acid, or the like upon which is superimposed a-primingcharge composed of one or 20 more of the initiating explosive mentioned hereinbefore. Blasting caps having non-initiating explosive charges are referred to in the art as caps containing 'a base charge and a priming charge and it is to this type of blasting cap that 25 this invention relates. The base charge-priming charge explosive charge may be used in either the open shell fuse or the closed shell electric blasting cap type of construction with equal success. The object of this invention is to produce an 3 improved base charge-priming charge comb-ination. for firing devices. A further object of this invention is to produce a blasting capwith a pentaerythritoltetranitrate base charge and having a priming charge which is less sensitive to 35 friction and impact than the previous priming charges used by the art. A still further object of this invention is to produce a fuse blasting cap of simple construction. Other objects will appear hereinafter.

In accordance with this invention there has been produced a blasting cap having'a base charge of pentaerythritoltetranitrate, and a priming charge of diazodinitrophenol alone or in admixture with an oxidizing agent such as potassium chlo- 45 rate. Further firing devices having a pentaerythritoltetranitrate base charge and a diazodinitrophenol or a diazodinitrophenol-potassium chlorate priming charge have been prepared in both the open fuse type shell and the closed elec so tric type shell blasting cap, and these various devices each show improvement over the pentaerythritoltetranitrate blasting caps oi? the art.'

Preferred embodiments of this invention have been chosen for the purpose of illustration and 55 description and are shown in the accompanying drawing forming part of the specification wherein,

Figure 1 is a cross-sectional view of an electric blasting cap, and

Figure 2 is a cross sectional view of a fuse is blasting cap.

Now in accordance with this invention there were prepared blasting caps of the open shell fuse type Figure 2 which contained a base charge (I) of about 0.23 gram of pentaerythritolteral0 nitrate pressed into the bottom of a .22 cal. shell; (2) 1 inches in length and superimpbsed upo this base charge (I) was pressed a priming charge (3) of about 0.38 gram oi diazqdinitrophenol-potassium chlorate 75/25 mixture. The 15 above blasting caps contained sufiicient explosive material to be classed as No. 6 caps according to the United States Bureau of Mines standards.

Another specific embodiment of this invention is a closed shell electric blasting cap Figure l which includes a base charge (4) of .BO'g-ram of pentaerythritoltetranitrate pressed into the bottom of a .30 cal. shell (5) 1% inches in length and superimposed upon this base charge a loose priming charge (6) of about 0.36 gram of diazodi- .nitrophenol-potassium chlorate 75/25 mixture.

Thee charged 'shells are then fitted with electric firing assemblies (7) comprisinga pair of leg wires (8) having a bridge wire (,9) across their ends and the said bridgewire (9) is-imbedded within the loose priming charge (6) andeach entire firing assembly (1) sealed into a cap shell (5) with a waterproofing compound (10) and sealing compound (I l). The above electric blasting caps containsuflicient explosive material to be classed as No. 6. caps according to the United States Bureau of Mines standard.

The caps prepared inaccordance with the above specific examples were tested by the standard sand bomb and {plate tests used by the art and were found tobe equivalent to the various No. 6 caps now available on the market in performance.

In accordance with this invention the priming charges of the specific examples given hereinbefore were composed'ofaniixture of diazo-. nitrophenol, 75%, and potassium chlorate, 25%, but such a mixture is not essential for an efilcient priming charge. Therefore it is to be under stood that diazodinitrophenol may be used alone as the priming charge for a pentaerythritoltectranitrate base charge or it may be used in suitable admixture with an oxidizing agent. The preferablev oxidizing agent for use in blasting caps is potassium chlorate and when this oxidizing agent is used in admixture with diazodinitrophenol the 75/25 diazodinitrophenol-potassium chlorate admixture used in the specific examples has been found to be the preferable priming mixture.

It will also be understood that by varying the weight of the pentaerythritoltetranitrate base charge the specific caps described can be manufactured to conform to any of the standard strength that may be desired. Further, as will be obvious to those skilled in the art, the quantities of explosives used as the base charge and priming charge for the specific examples given compare very favorably to the quantities of explosives used in most of the commercial caps of the art.

In the preparation of the above specific examples there were definite advantages derived from the use of diazodinitrophenol as the priming charge. for the pentaerythritoltetranitrate base charge over the use of mercury fulminate or leadv TABLE I Sensitivity to friction Maximum add- Explosive g g agg g ed weight for no explosions Cms. Ore. Diazodinitrophenol 50 More than 5000 Lead azide 50 1000 Mercury fulminate 50 25 Using the United States Bureau ol Mines Friction Pendulum Type B.

TABLE II Sensitivity to impact* of drop of 500 gr. weight for no Explosive I explosion C'ms. Diazodinitroph enol Lead azide Mercury iulminate- Using United States Bureau of Mines Small Impact Machine.

It is apparent from the results'in the above tables that blasting caps, containing a diazodinitrophenol priming charge superimposed upon a pentaerythritoltetranitrate I base charge, are much safer to manufacture and handle than the pentaerythritoltetranitrate blasting caps known to the art. Such anincrease of safety in' operation constitutes a major improvement in the explosive art. v

The fuse blasting caps prepared show further advantages and improvements over the blasting ,caps of theart; in that, when the pentaerythritoltetranitrate-diazodinitrophenol explosive charge given in the specific example hereinbefore described is used, a confining capsule for the priming charge is not required. Pentaerythritoltetranitrate blasting caps-containing mercury fulminate require the priming charge to be confined with' a capsule otherwise there is not suiiicient explosive force to properly detonate the base charge of pentaerythritoltetranitrate. It is also to be noted that the use of lead azide in open cop- Maximum height per shells is not recommended because copper azides will be formed and the copper azid'es are very sensitive and dangerous to handle. Lead azide is further relatively difiicult to ignite by the spit of a safety fuse and for this reason if lead azide is used in blasting caps, it is customary to place an ignition charge over the priming charge in order to insure ignition. The use of ignition charges is objectionable from the standpoint of economy and efiiciency.

While it is possible to use mercury fulminate in open shell caps having a pentaerythrltoltetranitrate base charge it is necessary to reinforce the mercury fulminate wth a capsule to insure the positive detonation of the pentaerythrltoltetranitrate base charge and whenever a capsule is used in a'bl asting cap, it is advisable to place an ignition or water charge above the capsule to insure ignition of the priming charge by the spit of the fuse. Here again such a device from the standpoint of economy and ebiciency shows disadvantages in comparison to the devices using a diazodinitrophenol priming charge and a pentaerythritoltetranitratebase charge.

The use .of diazodinitrophenol is, therefore. highly advantageous and provides the art with an improved pentaerythritoltetranitrate firing device from the standpoint of safety,.,economy and efiiciency of manufacture, positiveness of detonation, and simplicity of construction of the devices.

. It will be understood that the details and examples given hereinbefore are illustrative only and in no way limiting on my invention as broadly describe-d herinheiore and in the appended claims.

What I claim and desire to protect by Letters Patent is:

1. A firing device containing abase charge of pentaerythritoltetranitrate and a. priming charge of diazodinitrophenol superimposed thereon.

2. A firing device containing a base charge of pentaerythritoltetranitrate, and a priming charge of pentaerythritoltetranitrate, and a priming charge superimposed thereon which comprises an admixture o diazodinitrophenol, and an oxidiz ing agent.

.7. A firing device including a base charge of pentaerythritol tetranitrate and an unconfined priming charge of diazodinitrophenol superimposed thereon. p

8. A firing device including a base charge of pentaerythritol tetranitrate and an unconfined priming charge superimposed thereon which comprises an admixture of diazodinitrophenol and an oxidizing agent.

9. A firing device containing a. base charge of pentaerythritol tetranitrate and a priming charge superimposed thereon which comprises an admixture of diazodinitrophenoi and potassium priming charge superimposed thereon which chlorate. comprisesan admixture of diazodinitrophenol,

10. An electric blasting cap containing a base about 15%, and potassium chlorate, about 25%. charge of pentaerythritol tetranitrate and a 12. A firing device containing a base charge of 5 priming charge superimposed thereon w ch pehtaeiythritoi tetranitrate and an unconfined 5 comprises an admixture of diazodinitrophenol, priming charge superimposed thereon which about 75%, and potassium chlorate, about 25%. comprises an admixture of diazodinitrophenol 11. A fuse blasting cap containing a base and potassium chlorate. charge of gentaerythritoi tetranitrate and a WILLARD on 001mm. 

